73959-34-9Relevant academic research and scientific papers
Highly enantio- and s-trans C=C bond selective catalytic hydrogenation of cyclic enones: Alternative synthesis of (-)-menthol
Ohshima, Takashi,Tadaoka, Hiroshi,Hori, Kiyoto,Sayo, Noboru,Mashima, Kazushi
scheme or table, p. 2060 - 2066 (2009/04/07)
A highly enantioselective catalytic hydrogenation of cyclic enones was achieved by using the combination of a cationic Rh1 complex, (S)-5,5′-bis{di(3,5-di-tert-butyl-4-methoxyphenylphosphino)}-4, 4′-bi-1,3-benzodioxole (DTBM-SEGPHOS), and (CH2CH 2PPh3Br)2. The presence of an s-cis C=C bond isopropylidene moiety on the cyclic enone influenced the enantioselectivity of the hydrogenation. Thus, the hydrogenation of 3-alkyl-6-isopropylidene-2- cyclohexen-1-one, which contains both s-cis and s-trans enones, proceeded in excellent enantioselectivity (up to 98% ee). To obtain high enantio- and s-trans selectivities, the addition of a halogen source to the cationic Rh complex was the essential step. With the key step of the s-trans selective asymmetric hydrogenation of piperitenone, we demonstrated a new synthetic method for optically pure (-)-menthol via three atom-economical hydrogenations. Moreover, we found that the complete s-trans and s-cis C=C bond selective reactions were also realized by the proper choice of both the chiral ligands and halides.
Catalytic enantioselective conjugate addition of Grignard reagents to cyclic α,β-unsaturated carbonyl compounds
Kanai, Motomu,Nakagawa, Yuichi,Tomioka, Kiyoshi
, p. 3843 - 3854 (2007/10/03)
A catalytic asymmetric conjugate addition reaction of organocopper reagents, generated from copper salt, a chiral phosphine, and Grignard reagent, with cyclohexenone is highly dependent on the counter anion of copper species, solvents, Grignard reagents,
Catalytic asymmetric conjugate addition of Grignard reagents mediated by copper(I)-chiral bidentate phosphine complex
Kanai, Motomu,Tomioka, Kiyoshi
, p. 4275 - 4278 (2007/10/02)
A catalytic amount of a chiral phosphine I-copper iodide complex catalyzes the conjugate addition of organomagnesium chlorides to cycloalkenones and pentenolide to give the corresponding addition products in 94-72% ee.
Asymmetric Induction in Mn(III)-Based Oxidative Free-Radical Cyclizations of Phenylmenthyl Acetoacetates and 2,5-Dimethylpyrrolidine Acetoacetamides
Zhang, Qingwei,Mohan, Raju M.,Cook, Laura,Kazanis, Sophia,Peisach, Daniel,et al.
, p. 7640 - 7651 (2007/10/02)
Mn(III)-based oxidative free-radical cyclization of phenylmenthyl ester 1e afforded 90percent of 13 with 86percent de.Cyclization of 31b provided 56percent of (+)-podocarpic acid precursor 32e with 82percent de.The direction of de was opposite in these two cases.Oxidative cyclization of α-methyl β-keto ester 44b gave a 1:1.6 mixture of 46b and 47b while α-propyl β-keto ester 44d produced a >10:1 mixture of 46d and 47d indicating that the extent and direction of de is dependent on the size of the α-substituent.The reaction proceeds through transition states 12 and 56 with large α-substituents and through transition states 19 and 57 with small α-substituents.The de depends on the double-bond substitution pattern as shown by the decreased de with 37b and 37d, and selectivity in the 5-exo cyclization of 64b, 65b, 70b, and 71b is low.
